CARLTON tall forward Levi Casboult will miss six to eight weeks after suffering a hairline fracture in his left leg in the opening minutes of the Blues' two-point win against Port Adelaide.

The injury, which happened at the top of his tibia bone, does not require surgery.

While disappointing, the result was better than initially feared, when it seemed Casboult may have severely injured his knee.

Casboult hyperextended his knee after talking a contested mark over Tom Jonas, and was helped from the field by trainers.

Andrejs Everitt took the kick after the injury and put through a goal.

Television shots later in the first quarter showed Casboult in the Blues rooms with his knee iced, and no longer wearing his jumper.

He was No. 1 in the competition for contested marks coming into the game and has kicked six goals this season.